So, What Exactly is Ozone?
Ozone is actually a certain form of oxygen called O3. Oxygen makes up about 21% of the air that we breathe (with nitrogen accounting for most of the other 79%). Almost all of the oxygen in our air floats around in the form of something called O2. Although oxygen is basically a type of atom, these oxygen atoms prefer to form pairs which are molecules referred to as O2.
The reason that oxygen atoms form pairs is because the atoms on their own contain 2 “spare” electrons.
On their own, they will readily react with anything they can in order to share their spare electrons thus reacting with it and “oxidising” it. As it happens, there is another way to become stable. Basically, if two oxygen atoms share each other’s electrons then they both become happier and more stable. When this happens, the coupling together is called a “covalent bond” which is a little bit like two people holding hands. When two oxygen atoms form a covalent bond, they share their electrons between them.
Ozone, like O2, consists of oxygen atoms but instead of the molecule having just two oxygen atoms it has three. The first two atoms are very much in the covalent bond partnership; however, the third oxygen atom is a bit like a “hanger-on”. It is very weakly attached to the other two and will readily break off to go and “oxidise” any suitable passing molecule, particularly organic ones.
Ozone gives off a slight blue tint with a very pungent odour
Pure ozone is a blue gas with a distinct, pungent odour which smells a little like chlorine (the swimming pool smell). It is actually so pungent that we humans can detect it in air, even when it is in absolutely minute concentrations, as low as one part per billion. This same smell is often noticeable after a lightning storm because ozone is created whenever electrical arcing (or “sparking”) occurs through the air. It can also be created when UV light hits our atmosphere. Ever heard someone mention that the air always smells cleaner after a lightning storm? Well, now you know why!
Lightning storms create vast amounts of ozone, so much so you can smell it!
Nothing lasts for ever…
As mentioned before, the third oxygen atom in the arrangement is only weakly attached, which makes the molecule relatively unstable compared with O2. The third oxygen atom will very readily leave the molecule and join itself onto almost anything that comes close, thus oxidising it. In fact, the third atom is so weakly attached that, even if the O3 molecule does not come into contact with anything, the extra oxygen atom will eventually break off and leave to find another oxygen atom with which to form a stable O2 molecule.
Normal, untreated air has a “background” (or “naturally occurring”) level of ozone. In other words, there is a minuscule amount of ozone in the air that exists naturally. However, ozone has a half-life, just like a radioactive element like plutonium. What this means is that, if a volume of air is enriched with ozone then half of that ozone will decay into more stable O2 oxygen in a certain amount of time.
Ozone is oxygen just with a extra oxygen atom, this extra atom however has a weaker bond
This half-life time period varies somewhat depending on environmental factors such as humidity, temperature, pressure, dust levels and even the area of the surfaces in the surroundings that it could come into contact with. However, generally speaking, in a fairly normal environment, this half-life time is around 7-10 minutes. Even in clean air which has some ozone released into it, after approximately 7 to 10 minutes half of the ozone (O3) molecules will have broken down into O2.
Destruction by Oxidation!
Because of this “extra” oxygen atom, ozone is actually like a gaseous version of hydrogen peroxide (H2O2), which is a liquid. Hydrogen peroxide is water (H2O) but with a weakly attached extra oxygen atom which it readily gives up to any passing contaminant in liquid, be it a bacteria, a virus, a spore etc. Ozone works in a very similar way, but is a gas and destroys airborne contaminants instead.
Ozone works particularly well for destroying organic compounds which includes odour causing molecules and also microscopic pathogenic life such as bacterial infections and fungal spores. The ozone passes the weakly attached ozone atom to the offending particle/microbe and oxidises it. Oxidation destroys the original compound/microbe turning it into something else. By way of example, when something burns, it is actually going through the process of oxidation. I.e. the molecules or atoms of the thing which is burning are joining together with oxygen atoms (usually out of the air) to produce different molecules. Take a piece of wood, burn it, and you will end up with ash. The wood has been oxidised and the resulting ashes are made up of different (oxidised) chemical compounds.
As wood burns it turns to ashes, all thanks to oxidation
Interestingly, ozone can be pumped into water for disinfection purposes (the O’D-air G248 ozone generator can do this). However, when it is used in peroxide treated water, the two disinfection treatments join forces to become more potent than the sum of their individual parts. This reaction of ozone with peroxide creates something called “Peroxone” which promotes something called an “Advanced Oxidation Process”. Because of this highly energetic process, Peroxone is an extremely effective treatment for disinfecting water.
How Ozone can help us Growers
There are two main ways that ozone can benefit growers. First of all, it can help prevent airborne bacterial, viral and fungal plant infections from taking hold. Secondly, it can rid the air of odour causing organic molecules, which helps to eliminate those familiar plant smells as they grow and more importantly bloom.
Fungal infections, such as botrytis (commonly called grey mould or bud rot) and powdery mildew can be the bane of a grower’s life. Once either takes hold in one plant, they release spores into the air and the infection can spread like wildfire, infecting each and every plant. This can seriously affect productivity and quality. Also, bacteria can multiply on the surfaces of a plant tissues and then float around in the grow-space until they alight upon another plant surface, where they could cause more infection.
Ozone kills spores, bacteria and viruses on contact, leaving your grow room air sterile
Ozone will kill spores, bacteria and viruses upon contact helping to create a disease-free environment where plants can flourish. If a plant encounters disease, it will activate certain defence and immune systems to eliminate the threat. However, activating these systems requires energy which could otherwise be used for growth.
Diseases and insect infestations will, at least to some extent, slow down a plant’s growth. Energy that could have been used for growth is diverted into fighting the infection. It is a little bit like a body-builder that is suffering from a really bad bout of flu. The immune system of the body-builder is activated in order to fight the disease, and to do so it uses energy that could otherwise be used to increase the size of the body-builder’s muscles. When a plant senses it is being attacked, it can spur the plant on to grow faster because it senses that it needs to become fully grown and start reproducing as much as possible before it becomes severely diseased and compromised.
However, if a plant thinks that it is under attack but actually it isn’t, the extra incentive for the plant to grow, mature and reproduce is still activated but in reality the plant growth is not hampered by having to divert energy to actually fight an attack. For example, Ecothrive Charge and Halo activate the immune response by making the plant think it is under an attack. With its immune and defence systems activated, the plant attempts to accelerate towards being ready to reproduce and thus a growth spurt can ensue. However, with no actual infestation to waste energy on fighting, the plant uses all that extra energy to become more productive than ever before, all without actually being seriously impeded by an attack.
If ozone is used in a grow space, the chances of microbial infections are minimised to pretty much zero. This means that plants can use all of their energy to grow and reproduce. The use of ozone with the extra incentive from Ecothrive Charge or Halo can make a big difference to growth rates and final yields.
Healthy, disease-free plants produce an abundance of absolutely mouth-watering fruit…
Getting the dosage right!
Getting the right ozone level in your grow room is all down to the dosage. As mentioned before, it will readily oxidise anything that it encounters. In anything other than very low concentrations it can cause irritation to humans. For the sake of good health it is wise to keep within generally accepted guidelines. What is generally considered safe for humans is a concentration of up to 0.1 ppm, which works out at 0.2 milligrams of ozone in each cubic metre of air (0.2mg/m3). Or, to put another way, each milligram of ozone output per hour will easily treat (cleanse and disinfect) five cubic metres of space. To be on the safe side, let’s consider that each milligram of ozone output per hour is perfectly adequate (and safe) to treat 10 cubic metres of space.
There are two ways that that the majority of ozone generators work. Both are based on the principle of ionising oxygen molecules in the air (which is actually what happens during a lightning storm). The first method of production is with an ultraviolet (UV) lamp. When ultraviolet light passes through air, some of the oxygen (O2) is ionised. This ionisation causes some of the O2 to split up, and the resulting detached oxygen atoms latch onto O2 molecules, turning them into O3 ozone molecules. Using a UV lamp is a highly affordable way of producing ozone if it is only required in relatively small amounts. For large amounts of ozone production, many UV lamps would be required, making the resulting units bulky and impractical for large scale application.
For higher rates of ozone production you’ll need an ozone generator that uses something called a “corona discharge plate”. For this method, a high electrical charge is created on a discharge plate. Some of this charge “leaks” off into the air which ionises the oxygen in it. The ionised oxygen atoms then produce ozone in the same manner as a UV lamp would, but in greater amounts.
How to Work out the Ideal Output of an In-room Ozone Generator
If you want to use an in-room ozone generator, it is a good idea to get one that produces an appropriate level of ozone for the space you’re growing in. Without going into complex and in-depth mathematics, the maximum level of ozone that you ideally want is 0.1mg per hour for each cubic metre of the room. This guideline takes into account the decay rate of ozone in order to keep the level at about 0.2mg/hour.
For example, a large room which is 6 metres square and 2.2 metres high contains 6 x 6 x 2.2 = 79.2m3. So, 79.2 x 0.1 = 7.92mg/hour. In this scenario, an ozone generator that produces 7mg per hour would be the wise choice. If you would like to see a slightly more in-depth example of the maths involved with ozone dosage calculation then please see the bottom of this blog.
A Great Alternative to In-Room Generators
Many growers only consider using ozone in order to eradicate plant odour. Although, a quality carbon filter and extraction fan combination will do a good job of odour control, utilising ozone will ensure that all odours are destroyed and provides an extra level of safety and peace of mind. For this application, the ideal way to implement ozone is with an inline duct ozone generator.
An inline duct ozone generator fits directly into your extraction ducting, destroying any odour molecules which manage to survive carbon filtration. This method avoids filling the grow-space with too much ozone and utilises the great odour killing properties of ozone safely. When using an inline ozone generator it is important that the exit-end of the ducting is well away from where anyone might breath it in.
The new range of CarboAir in-duct ozone generators are carefully designed to produce an appropriate amount of ozone for the diameter of ducting that they are designed to be used with. The CarboAir in-duct ozone generators utilise a UV lamp in the narrowest of duct diameters while the units designed for wider duct diameters use a well calculated number of corona discharge plates.
Some History about Ozone
Ozone. Before 1985 it was a relatively uncommonly known word. Then, all of a sudden, something called the “Ozone Layer” became big news and the subject of international discussion.
The ozone layer protects the Earth from harmful UV radiation, allowing life to flourish
Apparently, this thing called the ozone layer, which surrounds our planet (some 12-20 miles up in the stratosphere) and has protected life on earth from the sun’s damaging UV rays for millions of years, had a hole growing in it above Antarctica. The hole in the ozone layer was caused by the release of certain chemicals into our atmosphere. These chemicals, some of which (among others) are called chlorofluorocarbons (also known as CFCs), that we humans were using in refrigeration and aerosol products, were being released into the atmosphere.
In 1987, an international agreement, called the Montreal Protocol, meant that the use of these ozone destroying chemicals was to be mostly phased out by the year 2000. Fortunately, now we have reached 2018, the ozone layer is reportedly healing and should be back to normal around 2050-2060.
A More In-depth Example of Calculated Ozone Requirements in a Room
As an example, let’s take a fairly typical small plug-in type generator which produces 7mg of ozone per hour. One of the smallest ones that we stock at One Stop Grow Shop only actually produces ozone for 3 minutes every 10 minutes. The 7 minute pause helps to prevent high concentrations of ozone from building up in the area around the generator. There are 6 x 10 minute slots per hour, so, this means that 1.16mg over 3 minutes every 10 minutes.
We can work out what volume of air we will be safe in but we need to take into account that roughly half of the ozone produced in a 3 minute burst will have broken down before the next 3 minute burst. As time goes by, the amount of ozone in the given volume of air in the environment will therefore rise. Strangely enough, the mathematics works through in such a way that because the half-life is around 7-10 minutes, the amount of ozone will approach and settle at roughly double with every 10 minute release rate.
So, 1.16 x 2 = 2.32mg. This means that if we divide that by the safe level we will arrive at the volume of air that this particular generator will be safe work alongside: So 2.32/0.2 = 70 m3. If we assume an average grow-space height to be 2.2 metres then this means that the area it can be used in is 70/2.2 = 31.8 m2. To get an idea of how large that is, we can take the square root of this area to find the length of the sides of a square area of this size: √31.8 = 5.64m. So, this generator would be generally considered safe a room 5.7m x 5.7m x 2.2m. However, if there a lot of items which take up space then the volume of the room needs to be larger.
So to summarise the calculation:
- Find the volume of your room in m3 (cubic metres) by multiplying Height x Width x Depth (all measured in metres) = V
- Divide V by 10 to find the amount of mg/hour you will need. So: Ozone/Hour = V / 10